BEING BILLED FOR SOMETHING I SHOULDNT BE PAYING FOR

i was asked to change my subscription to the BIZTALK 400 and it would work out cheaper as you receive 400min, however i am being charged R350.00 for this package and overall usage for calls R261.00 - day light ******* if you dont read your bill - you just pay what they say my bill is over R1000.00 - and yet taking this subscription my bill was meant to be reduced. when you call the billing division - nobody can assist, they merely log the call and dispute i was asked to pay the full amount and if its incorrect then telkom will refund the R261.00, every cent counts and nobody just has extra R200 in their wallet to just pay. i got told they will call me back within 7-14 days, the bill is due before the end of the month and if you late with payment then you charged R9.72 - in actual fact that shouldnt even be my problem, i will only pay what i owe nothing more - nothing less. and if they dont call then i must phone them, how ridiculous! very disappointed in this type of service